Process for stabilized ethylenically unsaturated beta-hydroxy esters

ABSTRACT

An ethylenically unsaturated beta-hydroxy ester stabilized to gel formation but which remains susceptible to polymerization by ionizing radiation is obtained by reacting a polyepoxide with an alpha, beta-ethylenically unsaturated carboxylic acid such as acrylic or methacrylic acid in the presence of a tin halide salt.

United States Patent n91 Field of 260/486 B Radlove Nov. 18, 1975 [54] PRocFssFoR STABILIZElY 56 References Cited ETHYLENICALLY UNSATURATED" v UNITED STATES PATENTS BETA'MDROXY'ESTERS r 3,373,075 3/1968 Fekete'et all 260/486 B [75] lnventorz B. Radlove, Chicago, Ill. 3,708,524 l/ 1973 Murayama 260/486 B 73 Assi nee: Continental C an In Q i 1 New York romp c Primary Examiner-Lorraine A. Weinberger Assistant EXaminerPaul J. Killos H Filed: I y I Attorney, Agent, or FirmPaul Shapiro; Joseph E. 2 1 App] 7 6 Kerwin; William A. Dittmann v Related U.S. Application Data i v v {63], Continuation of Ser. No. 306,106, Nov. :13, 1972, 1 v. ABSIRACT 4 abandoned, which is" a continuation-impart of 'Ser. An ethylenically unsaturated beta-hydroxy ester stabi- 242,777, April 10, 1972, albandolied;v 5 lized to gel formation but which remains susceptible to v [polymerization by ionizing radiation is obtained by re-. Cl 260/486 0/4 260/ 105; v acting a polyepoxide with an a1pha, beta-ethylenically 260/488 J; 260/488 CD' unsaturated 'carboxylic acid such as acrylic or meth- Int.'Cl. C01C 69/54 acrylic acidin the-presence of a tin halide salt.

7 Claims, No Drawings PROCESS FOR STABILIZED ETHYLENICALLY UNSATURATED BETA-HYDROXY ESTERS This application is a continuation of Ser. No. 306,106, filed Nov. 13, 1972, now abandoned, which is a continuation-in-part of application Ser. NO. 242,777, filed Apr. 10, 1972, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention is related to ethylenically unsaturated beta-hydroxy ester compositions and more particularly, to stabilized beta-hydroxy ester compositions susceptible to polymerization using ionizing radiation.

2. The Prior Act Printing or decorating metal substrates is conventionally accomplished using inks composed predominately of a drying oil vehicle pigmented to the desired color which is dried by baking-in air. Conventional printing inks prepared with drying oil vehicles contain a substantial amount of a volatile organic solvent which must be removed as the ink dries. The evaporation of the solvent creates an air pollution problem which many present day communities will not tolerate.

One method of avoiding the use of solvents in preparing printing ink vehicles which has been attempted by the art is to prepare the vehicle from an unsaturated polyester composition of suitable viscosity which can be polymerized and dried by exposure to ionizing radiation as for example, U.S. Pat. Nos. 3,326,710, 3,511,687, 3,551,235, 3,551,246, 3,551,311, and

One class of unsaturated compositions which is particularly suitable as radiation curable ink vehicle components is the ethylenically unsaturated beta-hydroxy esters. Ethylenically unsaturated beta-hydroxy esters are known to the art and are prepared by reacting a polyepoxide having at least two reactive epoxide groups with an alpha, beta-ethylenically unsaturated carboxylic acid.

Heretofore, ethylenically unsaturated beta-hydroxy esters have been prepared through the use of tertiary amines as a catalyst e.g., U.S. Pat. No. 2,824,851 with the inclusion of a vinyl polymerization inhibitor such as hydroquinone. The storage life of such ester products has been limited as the esters are very reactive monomeric materials and form useless gels when stored for short periods, i.e., within 1 month's time. The presence of vinyl polymerization inhibitors in the ester product interferes with the sensitivity of the ester toward polymerization with ionizing radiation and the removal of the inhibitor from the ester reaction product is a difficult and costly procedure.

Although the art has proposed the addition of stabilizing agents to the ethylenically unsaturated betahydroxy ester compositions to stabilize the compositions to premature gelation, e.g., U.S. Pat. No. 3,408,422, in many cases the addition of such agents further diminishes the sensitivity of the ester toward ionizing radiation, thereby reducing the utility of the unsaturated esters as radiation curable compositions.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a method for preparing an ethylenically unsatu rated beta-hydroxy ester composition which is stable to premature gel formation and which is sensitive to rapid polymerization by exposure to a source of ionizing radi- 2 ation wherein the reaction between the polyepoxide and the alpha, beta-ethylenically unsaturated carboxylic acid to form the beta-hydroxy ester is conducted in the presence of a tin halide salt.

Ethylenically unsaturated beta-hydroxy esters p're- PREFERRED EMBODIMENTS Typical tin salts that may be employed in the process of the present invention include the tin halide salts such as SnCl The amount of tin salt incorporated in the reaction mixture may vary over a considerable range. In general, the amount of tin salt will vary from about 0.10% to about 3.0% .by weight of the reactants involved in the ester forming reaction and more preferably from about 0.2% to about 0.6% by weight of the reactants.

The reaction to prepare the ethylenicallyunsaturated beta-hydroxy ester includes alkaline catalysts such as tertiary amines, quarternary ammonium hydroxides, quarternary ammonium halides, benzyl trimethyl ammonium hydroxide, N, N'-dimethylanline, N, N-benzyl dimethyl amine, potassium hydroxide, or lithium hydroxide to accelerate the rate of reaction.

The amount of catalyst incorporated in the reaction I mixture may vary over a considerable range. In general, the amount of the catalyst will vary from about 0.2% to about 2.0% by weight and more preferably from 0.6% to 0.8% by weight of the reactants.

The reaction to prepare the gel stable ethylenically unsaturated beta-hydroxy ester may be conducted in the presence or absence of solvents or diluents. In cases where the reactants are liquid, the reaction may beeffected in the absence of solvents. When either or both reactants are solids or viscous liquids, it may be desirable to add solvents to assist in effecting the reaction.

Examples of suitable solvents include inert organic liquids such as ketones, such as methyl ethyl ketone, hydrocarbons such as cyclohexane and aromatic solvents such as toluene and xylene.

Temperatures employed in the reaction to form the beta-hydroxy ester will generally vary from about 50 to 150C and preferably about to C. The reaction is conducted under an inert atmosphere such as nitrogen, and may be conducted at atmospheric orreduced pressure under reflux conditions.

The reaction to form the beta-hydroxy ester requires about a l to 10 hour period to be completed or until the alpha, beta-ethylenically unsaturated carboxylic acid is substantially consumed. The course of the reaction may be conveniently followed by a determination of the acidity. The reaction is considered to be substantially complete when the acidity has been reduced to an acid number of 10 or less.

After the reaction to form the beta-hydroxy ester is completed, if desired, the tin salt may be inactivated in the ester product by reacting the ester product with 85%-95% phosphoric acid. In effecting inactivation of the salt, the acid is added to the ester reaction product at a concentration of 0.1% to 0.2% based on the weight of the ester and heated at 25 to 40C for 0.5 to 2 hours whereupon an insoluble colloidal solid can be separated from the reaction product by filtration or other above described and commercially available from the Dow Chemical Company, n is zero.

Aliphatic polyepoxides are the reaction products of ephihalohydrins with aliphatic polyhydric alcohols simple separation technique or may be allowed to re 5 such as trimethylol ethane, glycerol, pentaerythritol, main in the reaction product. sorbitol, trimethylol propane, erythritol, arabitol, man- The proportions of ethylenically unsaturated alpha, nitol, trimethylene glycol, tetramethylene glycol, ethylbeta-carboxylic acid and polyepoxide employed in preene glycol, polyethylene glycol, propylene glycol, polyparing the ethylenically unsaturated beta-hydroxy ester propylene glycol, butylene glycol, polybutylene glycol compositions of the present invention is not critical. In and the like. general, a molar equivalent of polyepoxide is utilized RD-2, the diglycidyl ether of 1,4 butylene glycol, for l to 2 molar equivalents of the ethylenically unsatumanufactured by Ciba is an example of a commercially rated carboxylic acid. available aliphatic polyepoxide.

The alpha, beta-ethylenically unsaturated carboxylic The stabilized ethylenically unsaturated betaacids which may be reacted with the polyepoxide to 5 hydroxy ester compositions prepared by the process of prepare the beta-hydroxy esters in accordance with the the present invention are useful as radiation curable process of the present invention include the monocarcoating materials for coating a variety of substrates boxylic acids having three to six carbon atoms suchas such as metal, paper, and wood. The stabilized ester acrylic acid, methacrylic acid, eth acrylic acid and cromay be used alone or in combination with other unsatutonic acid. Of these acrylic and methacrylic acids are rated compounds such as vinyl monomers and the like. preferred. in preparing the beta-hydroxy esters, a por- The stabilized beta-hydroxy esters are particularly tion of these unsaturated acids may be replaced by satuseful as components of printing ink vehicles which are urated acids having three to l8 carbon atoms such as curable by ultraviolet radiation. In preparing such caprylic, pelargonic, palmitic, and the like to vary the printing ink vehicles the stabilized ethylenically unsatuphysical properties of the beta-hydroxy ester. The saturated beta-hydroxy ester is advantageously admixed rated acid may be incorporated in the reaction medium with at least one other ethylenically unsaturated polyat a concentration that does not exceed 25 mole perester such as polyacrylates and polyitaconates, and a cent of the total acid and is generally in the range of photosensitizer. about 5 to about 20 mole percent. Polyacrylates are prepared from a polyhydric alcohol The polyepoxides used to prepare the beta-hydroxy having from two to six hydroxyl groups and an alpha, esters in the practice of the present invention comprise beta-ethylenically unsaturated monocarboxylic 'acid all those organic compounds containing at least two rehaving from three to six carbon atoms, generally 50 to active epoxy groups, i.e., 100 percent of the hydroxy groups being esterfied with the'ethylenically unsaturated monocarboxylic acid.

0 Illustrative polyhydric alcohols which may be used to prepare polyacrylates include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol,

- diethylene glycol, butanediol, trimethylolethane, trigroups in their molecule- The polyepoxides y be methylolpropane, trimethylolhexane, glycerol, manniurated or unsaturated, aliphatic, cycloaliphatic, aro- 40 t n h iml d i t f th l h d i matic, or heterocylic and may be substituted if desired l ohol with non-interfering SubStituentS- Unsaturated monocarboxylic acids which may be re- Aromatic polyepoxides are the polymeric reaction acted with the polyhydric alcohols to prepare the polyproducts of polyhydric mono and polynuclear phenols acrylates include acrylic acid, methacrylic acid and with polyfunctional halohydrins and/or glycerol dichloh l li id, rohydrin- A l rg n m of p ly p xi f hi yp The polyitaconates are prepared by reacting 0.8 to l are disclosed in the Greenlee patents, US. Pat- N mole itaconic acid with l to 1.2 moles by an aliphatic 2,585,l l5 and 2,5 89,245. In additi n many f th s or aromatic polyepoxide or a mixture thereof, preferaresins are commercial products. Typical polyhydroxy bly in the presence of a small amount of a saturated di- Phenols useful in the Preparation ofal'omatie P Y P basic acid containing 20 to 40 carbon atoms, such as ides include resorcinol and various diphenols resulting h C di dd prepared b h polymerization f from th n nsati n f ph n l with aldehydes and C, unsaturated fatty acids. The amount of saturated ketones u h as formaldehy l hy acetone, dicarboxylic incorporated in the polyitaconate reaction methyl ethyl ketone and the like. A typical aromatic mixture is generally in the range of 5 to 15 mole perpolyepoxide is the reaction product of epichlorohydrin cent b d on th it oni a id, 4 a (P- Y Y P y p p (Bisphenol Photosensitizers found to be particularly useful in the resin havingthe f l g Structural formula; sensitizing the beta-hydroxy ester are derivatives of anwherein n is zero or an integer up to 10. Generally speaking, n will be no greater than 2 or 3 and is preferably l or less.

In DER 332, an aromatic polyepoxide of the type thraquinones such as l-chloro, 2-chloro, Z-methyl, 2- ethyl and l-chloro-2-methyl, anthraquinone.

Rapid ultraviolet curable printing ink vehicles particularly suitable for application to metal substrates contain 30 to 65% byweight, and preferably-40 to 50% by weight-of the-=beta-hydroxy vester, 2 to by weight.

weightof the polyacrylate or mixtures thereof and 0.10,,

to 5% weight and preferably 0.5 to 1.5 by weight of the I I photosensitizier;

In general, printing inksprepared using radiation cun positions were also tested forgel stability. The results able vehicles are-prepared in t-hesame manner as conventional printing inks only using the vehiclecompo- I nents asdisc-losed herein..Generally the printing inks contain about 30 to about 80 percent by weight of the I vehicle and about to 70 percentby weight ofapigment such asTiO In printing metal surfaces',' with radiation curablej printing inks, the ink is applied using a printing press conventionally used for printing on'a metal substrate.

Once the metal substrate, generally inrthefo rrn of a I sheet, is printed, the substrate is positioned to pass under s source of ultravioletlightto cure and dry the ink. In most instances, the ultravioletv lightsource is maintained at about 0.5 to about 5 inches from the printed substrate undergoing irradiation.

Rapid drying of theink is effected within a 0.5 to 2.0 'second period using ultraviolet light emitted from an artificial source having a wavelength in the range between 4000A and 1800A. The output of commercially available ultraviolet lamps generally vary between 100 watt/in. to 200 watt/in. of lamp surface.

High pressure mercury vapor discharge lamps of quartz are the preferred source of ultraviolet light.

Medium-pressure mercury vapor discharge lamps of 'EXAMPLEI To a reaction vessel, equipped with a condenser, stirrer, thermometer, and nitrogen inlet tube was charged the following reactants:

Bisphenol A Diglycidyl ether (DER 332) 400 grams 4 v (1.15M) Glacial acrylic acid 132.8 grams Pelargonic acid 31.6 grams Benzyl dimethyl amine 4.0 grams Stannous chloride (in 50 mls.

2.0 grams methylethyl ketone) .The temperature of the reaction mixture was raised to and maintainedv at 102C for 4.0 hours under nitrogen atmosphere. Titration of a sample of the reaction mixture with a 0.2N alcoholic KOH solution at this.

time indicated that the reaction mixture had an acid value of 1.4 indicating substantially complete reaction of the bisphenol ether with the acrylic acid. The resultant reaction product was a pale slightly cloudy solution. The bisphenol ether/acrylic acid ester reaction mixture was then treated withl gram of 86.7% H P0 in 100 ml. methylethyl ketone and stirred for 1 hour at room temperature to inactivate the SnCl, and neutral ize the catalyst.

' watts/in. of lamp surface. The conveyor was adjusted so A portion of the inactivated reaction mixture was;

placed in a brown bottle and examined periodically for of these comparison tests designa 6 evidence of gel formation. The gel stability is recorded in the Table below.

For purposes of comparison, ina-separate series of reactions, ,the procedure of the Example was repea ted witlithe exception that either SnCl, was not used, the benzyl dimethyl amine catalyst was not employed, or some metal chloride salt other than .SnCl was incorporated in the reaction mixture. These comparison comted by thegsyiirbol C? are also summarized the Table v a TABLE 1 TEST STABI- OBSERVATIONS GEL NO. :LlZER I STABILITY V (weeks) I N, nCl,. over 28 Cf none "Reaction product gelled during.

, preparation. C S nCl' No catalyst*' 4 C CtiCl Reaction product'gelled during preparation. C 3 Reaction product gelled ZnCl,

during preparation.

Acid number 163 indicates large amount of acrylic acid unreacted.

A white ink was prepared on a three roll mill using 50% of a titanium dioxide pigment and 50% of an ink vehicle including the beta-hydroxy ester prepared 1 above, the vehicle having the following composition:

COMPONENT WEIGHT PERCENT Beta-hydroxy ester 44.! Polyitaconate* 4.4 Polyethylene glycol**diacrylate 11.0 Pentaerythritol tetraacrylate 39.6 l-chloro-Z-methyl anthraquinone V 0.9

Reaction product of 0.6 moles DER 332, 0.25 moles RD-Z. 0.7 moles itaconic acid and .075 moles C, dimer acid. .Molecular weight 200.

The ink had a tack of 31.

Using aconventional lithographic technique (ATF Chief 20 A'printing press) the white ink was printed upon the surface of 5 X 3 inch steelplates of the type used in the manufacture of metal cans- I After application of the printing, the printed plates were placed on a continuously moving conveyor which passed under a bank of three- 12 inch, high pressure mercury lamps mounted parallel to each other. The radiation emitted by the lamps was approximately that the coatedplates traveled under the surface of the ultraviolet'lamp bank so that the plates were 1.0 inch fromthe lamp surface. The speed of the conveyor belt was adjusted so that the printed plates were exposed to the ultraviolet radiation for about 2 seconds whereby total drying of the plate was effected.

EXAMPLE II COMPONENT WEIGHT PERCENT Beta-hydroxy ester 49.0 Polyitaconate 6.0 Polyethylene glycol diacrylate 6.5 Pentaerythritol tetraacrylate 37.5 l-chloro. Z-methyl anthraquinone 1.0

unsaturated carboxylic acid having three to six carbon atoms is reacted in the presence of an alkaline catalyst, wherein the improvement comprises incorporating in the mixture a small but effective amount of a tin halide salt to prepare the beta-hydroxy ester which is stable to premature gelation.

2. The method of claim 1 wherein the polyepoxide is the diglycidyl ether of Bisphenol A.

3. The method of claim 1 wherein the acid is acrylic acid.

4. The method of claim 1 wherein the tin halide salt is SnCl 5. The method of claim 1 wherein the catalyst is a tertiary amine.

6. The method of claim 5 wherein the tertiary amine is N,N' benzyl dimethyl amine.

7. The method of claim 1 wherein the tin salt is present in the mixture at a concentration of 0.1% to 1.0% by weight. 

1. IN THE METHOD OF PREPARING AN ETHYLENICALLY UNSATURATED BETA-HYDROXY ESTER SUSCEPTIBLE OF POLYMERIZATION BY ULTRAVIOLET RADIATION WHEREIN A MIXTURE OF A POLYEPOXIDE HAVING AT LEAST TWO EXPOXIDE GROUPS IN THE POLYEPOXIDE MOLECULES AND AN ALPHA, BETA-ETHYLENICALLY UNSATURATED CARBOXYLIC ACID HAVING THREE TO SIX CARBON ATOMS IS REACTED IN THE PRESENCE OF AN ALKALINE CATALYST WHEREIN THE IMPROVEMENT COMPRISES INCORPORATING IN THE MIXTURE A SMALL BUT EFFECTIVE AMOUNT OF A TIN HALIDE SALT TO PREPARE THE BETA-HYDROXY ESTER WHICH IS STABLE TO PREMATURE GELATION.
 2. The method of claim 1 wherein the polyepoxide is the diglycidyl ether of Bisphenol A.
 3. The method of claim 1 wherein the acid is acrylic acid.
 4. The method of claim 1 wherein the tin halide salt is SnCl2.
 5. The method of claim 1 wherein the catalyst is a tertiary amine.
 6. The method of claim 5 wherein the tertiary amine is N,N'' benzyl dimethyl amine.
 7. The method of claim 1 wherein the tin salt is present in the mixture at a concentration of 0.1% to 1.0% by weight. 